Not Applicable.
Not Applicable.
Oxygen concentrators have been available for many years as a source of oxygen enriched air for patients requiring supplemental oxygen. The oxygen concentrator includes a filter element which passes oxygen while blocking the flow of nitrogen. This will typically result in a gas which is up to about 95% pure oxygen, with at maximum separation efficiency the remainder of the gas being primarily argon. An oxygen concentrator is not designed for portable applications because of its size, weight and power requirements. Typically, an ambulatory patient requiring supplemental oxygen will carry a relatively small container containing either compressed gaseous oxygen or liquefied oxygen. In the past, the portable compressed gaseous oxygen cylinders were filled from a larger container of compressed oxygen. The system may include a flow controller which delivers oxygen pulses only during inspiration to conserve oxygen and thus prolong the ambulatory time for the patient. Recently, oxygen concentrators have sometimes been provided with a compressor suitable for compressing the oxygen enriched air sufficiently for filling a portable oxygen cylinder. Another recent development is apparatus which cools and liquefies the oxygen enriched air from an oxygen concentrator for filling portable liquid oxygen containers.
When oxygen is to be breathed by a patient, it is critical that the oxygen not be contaminated. If a portable oxygen cylinder is completely empty prior to filling, there is a risk that the cylinder valve may have been left open and that the interior of the cylinder has become contaminated. For patient safety, it is necessary that an empty oxygen cylinder be cleaned and flushed with oxygen prior to filling to remove any possible contaminants that may have entered the cylinder. To avoid this problem, the Compressed Gas Association has recommended that gaseous oxygen cylinders not be emptied below 25 psig. The Association recommends that the tank pressure be manually checked prior to filling.
U.S. Pat. No. 4,856,284 to Mattiola et al. discloses a system for automatically filling a liquid gas cylinder. Prior to filling the cylinder, the cylinder is evacuated. As gas is evacuated from the cylinder, it is automatically analyzed for contamination to prevent filling a contaminated cylinder.
The invention is directed to an oxygen concentrator which is capably of supplying oxygen enriched air of from about 85% to about 95% oxygen concentration to a patient and/or to a compressor or a cooler for filling a portable gaseous or liquid oxygen cylinder for use by an ambulatory patient. The oxygen concentrator includes a programmed cycle for automatically filling the oxygen cylinder to a programmed maximum pressure. The cylinder pressure is constantly monitored during the fill cycle. According to the invention, the initial cylinder pressure is compared with a programmed minimum acceptable pressure, such as 100 psig. If the cylinder pressure falls below the programmed minimum acceptable pressure, the oxygen concentrator is prevented from filling the cylinder. Consequently, an empty cylinder which may be contaminated cannot be filled. The patient must take the empty cylinder to a dealer who is qualified to check for contaminants prior to filling the cylinder.
Accordingly, it is an object of the invention to provide a cylinder filling oxygen concentrator which cannot automatically fill an empty oxygen cylinder which may be contaminated.
Other objects and advantages of the invention will become apparent from the following detailed description of the invention and the accompanying drawings.